The Automatic switched optical network (ASON) is a new-generation optical transmission network capable of accomplishing the switching and interconnection functions of the optical network intelligently and automatically. The ASON is a high flexible and expansible fundamental optical network facility, using software as core and capable of providing calls from the optical layer directly according to the service demands of network and users. The ASON is formed by integrating the flexibility and efficiency of the Internet Protocol (IP), the protection capability of the Synchronous Digital Hierarchy (SDH)/the Synchronous Optical Network (SONET) and the capacity of the Dense Wavelength Division Multiplexing (DWDM) through the innovative distributed network management system.
WSON is an ASON system based on the DWDM device. The automatic switching and connection function of the system is accomplished on the basis of the automatic discovery of network resource and topological structure by calling the dynamic intelligent routing algorithm and using distributed signaling processing and interaction to establish connections between network nodes based on demands, at the same time a protection restoration mechanism can be provided to accomplish the automatic reorganization under a fault situation.
In the WSON system, a mismatch of the same wavelength resource states between adjacent network-element devices can be caused by the situation of signaling loss or node restarting when a call deletion command is sent, etc. Namely: the states of the receiving end and sending end are inconsistent. The mismatch of the wavelength resource states may lead to an occupation of the link bandwidth resource on the node device when relative call is no longer exist. If it is not processed in time, in the situation that call are established and deleted repeatedly or the mismatch of the resource states has occurred several times, it will make the call unestablishable even the bandwidth resource is available. When such fault occurs, there is no effective way to release the related resource, the only method available is to clear up the configuration database through the node and reset it, but this method may cause interruptions to all the calls going through this node and also the losing of call information, which will bring great loss to the operators.